Washington: Republican presidential challenger Mitt Romney on Sunday accused President Barack Obama of running a negative and divisive campaign against him, and charged that the incumbent's policies were "weakening America in very fundamental ways".

Romney said Obama's campaign managers were indulging in character assassination and were dividing Americans through their electoral campaign.

"I think this president is weakening America in very fundamental ways. And a lot of people are suffering for it now. Over the coming decade, the decisions he's making will cause a lot more people to suffer," Romney told media in an interview.

The former Massachusetts Governor will formally accept the Republican nomination for the November presidential elections at the party's national convention in Tampa next week.

He said he looked at the nomination and his electoral fight as an opportunity to get the US "on track again".

"If I can (win), I want to make sure that we get the country back on track," he said.

"I feel like, wow, a lot of people are counting on me. They're hoping I'll be able to win and I'll be able to get America on track again," he added.

Romney accused Obama of running a campaign of "anger and divisiveness", that pitting one street against another, and pointed out that this campaign of "character assassination" is very different from the campaign of hope and change which he ran on originally.

"I think his whole campaign he's been about dividing the American people. It's between the haves and the have-nots, the people of one location versus another," he said.

"This is one street versus another street. That's the kind of divisiveness that I think Americans recognise and I think it's one of the reasons why his campaign, despite spending massively more than our campaign, that his campaign hasn't gained the traction that he would have expected," he said.

Romney strongly refuted allegations that he evaded taxes by having account in Swiss banks or overseas.

"There was no reduction, not one dollar of reduction in taxes, by virtue of having an account in Switzerland or a Cayman Islands investment. Those dollars of taxes remained exactly the same. There was no tax savings at all," he said.

"And the conduct of the trustee in making investments was entirely consist with US law and all the taxes paid were those legally owed and there was no tax savings by virtue of those entities," he asserted.

"But they're trying to make that seem like it's some a unsavory action. And, frankly, all the taxes were paid exactly as owed and there was no tax savings by virtue of having that vehicle," Romney said.